The invention relates generally to a wind turbine generator and more specifically to a structure for reducing the size and weight of the brake for the wind turbine generator.
Generally, wind turbines use the wind to generate electricity. The wind turns multiple blades connected to a rotor. The spin of the blades caused by the wind spins a shaft of the rotor, which connects to a generator that generates electricity. Specifically, the rotor is mounted within a housing or nacelle, which is positioned on top of a truss or tubular tower, which may be as high as about 100 meters. Utility grade wind turbines (e.g., wind turbines designed to provide electrical power to a utility grid) can have large rotors (e.g., 50 or more meters in diameter). Blades on these rotors transform wind energy into a rotational torque or force that drives one or more generators, rotationally coupled to the rotor through a gearbox. The gearbox may be used to step up the inherently low rotational speed of the turbine rotor for the generator to efficiently convert mechanical energy to electrical energy, which is provided to a utility grid. Various types of electrical generators may be used in these wind turbines.
To accommodate the need for greater power from windfarms, individual wind turbine generators are increasingly being provided with higher power output capability. In general, to accommodate a higher power output, the power generating equipment including electrical generator, gearbox and controls become larger and heavier. However, due to the location of in the nacelle at the top of a tall, thin tower, limiting the weight and size for the power generating equipment such as the wind turbine generator and the gearbox becomes critical.
FIG. 1 illustrates a prior art power train 105 for a wind turbine 100 within nacelle 185 atop tower 190. Rotor hub 110 is driven by the wind turbine blades (not shown) to turn wind turbine rotor shaft 175 supported by main bearing 125. Gearbox 160 is tied to drive wind turbine generator 150 through coupling 165.
A braking mechanism typically is provided for the wind turbine generator (WTG). The braking mechanism may be used to stop the rotor from spinning and to hold the rotor after it has been stopped. Often the brake for the WTG is a disc-type brake.
FIG. 2 illustrates a simplified arrangement for a typical prior art disc brake structure for a wind turbine generator. Multiple wind turbine blades 220 are attached to a rotor hub 210. A main shaft 230 from the hub 210 is tied to a gearbox 240. An output shaft 250 from the gearbox 240 drives the rotor shaft (internal) to wind turbine generator 260. Situated between the gearbox 240 and the wind turbine generator 260 on the gearbox output shaft 240 is a disc brake 270. The disc brake 270 includes a cylindrical brake disc 275 on the gearbox output shaft 250 and a brake calipers 280 (mounting not shown). Although only one brake caliper 280 is shown, a plurality of brake calipers may be mounted circumferentially around outer radial end surfaces 285 of the cylindrical brake disc 275.
The brake disc 275 may typically be about 0.8 m to 1.2 m in diameter, with a thickness of about 25 mm to 50 mm thick. The disc may weigh about 100 kg to 500 kg, a substantial weight considering the height the wind turbine tower from the ground. The weight of the brake disc 275 can be a significant load for bearing supports for the power train. Further, the positioning of the brake disc between the gearbox and the generator adds length to overall axial size of the power train. The positioning of the brake disc 275 adjacent to an end 255 of the wind turbine generator 260 may also restrict access to the internals (not shown) of the wind turbine generator 260. Such limits on access may make maintenance on the internals of the wind turbine generator 260 more difficult.
Accordingly, there is a need to provide a braking system within a WTG structure that reduces the size, weight and overall length of the power train, while at the same time providing enhanced access to the generator casing internals.